Erectile dysfunction (ED) or impotence is a sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual activity. A penile erection is the hydraulic effect of blood entering and being retained in sponge-like bodies within the penis. The process is most often initiated as a result of sexual arousal, when signals are transmitted from the brain to nerves in the penis. The most important organic causes are cardiovascular disease and diabetes, neurological problems (for example, trauma from prostatectomy surgery), hormonal insufficiencies (hypogonadism) and drug side effects.
The study of ED within medicine is covered by andrology, a sub-field within urology. Research indicates that ED is common, and it is suggested that approximately 40% of males suffer from ED or impotence, at least occasionally. Current treatments for ED include drugs such as, for example, vardenafil, avanafil, sildenafil, tadalafil, and alprostadil. Furthermore, there are studies suggesting that natural herbals, such as damiana, horny goat weed, and yohimbine, are also effective in treating ED.